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Evaluation of a microcomputer‐based control system for a domestic sized engine‐driven water‐to‐water heat pump
Author(s) -
Welsby P.,
Diggory P. J.,
Devotta S.
Publication year - 1988
Publication title -
international journal of energy research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.808
H-Index - 95
eISSN - 1099-114X
pISSN - 0363-907X
DOI - 10.1002/er.4440120209
Subject(s) - superheating , heat sink , air source heat pumps , heat pump , coefficient of performance , thermal expansion valve , hybrid heat , working fluid , heat capacity rate , mechanics , mechanical engineering , heat engine , materials science , environmental science , control theory (sociology) , heat spreader , thermodynamics , engineering , evaporator , computer science , heat exchanger , physics , control (management) , artificial intelligence
Steady‐state performance data have been obtained on a domestic sized engine‐driven water‐to‐water heat pump. The optimum working fluid suction superheat for the system was found to be 12°C. Over a range of heat sink conditions, increasing the engine speed linearly increased the total heat prouduced by the unit. Similarly, over a range of heat source conditions, increasing the engine speed linearly increased the working fluid evaporation rate. To produce water at 80°C, the heat pump was designed to operate with a heat sink temperature of 70°C, but its efficiency was improved by operating with the heat sink at 55°C. With a heat sink temperature of 55°C the primary energy ratio of the unit was observed to vary from 0–85 to 1–16, over a range of heat source temperatures. Algorithms developed from the steady‐state experiments were incorporated as control function subroutines in a microcomputer program. Using this program, the microcomputer was employed to control the heat pump outlet water temperature and the working fluid suction superheat. The control system was tested in a series of dynamic experiments and was found to operate effectively and achieved its control requirements. In certain tests, the transient time period was extended because the electrically‐controlled expansion valve was too large for the system and created instability in the suction superheat.